Add test for reading/writing multiple audio formats

[gavv]

After merging #660, add a test to test_pump.cpp that is the same as write_read, but instead of checking only wav files, it should check all supported formats (mp3, aiff, etc).

The new test should:

• invoke IBackend::discover_drivers()
• find all file formats supported by backend (use DriverInfo::type to distinguish if given driver is a file format)
• and perform the test for each of such formats

In other words, the test iterates over all backends, for each backend it iterates over all file formats, and for each such pair of backend+format it performs the same check as implemented in write_read test.

Doc: https://github.com/roc-streaming/roc-toolkit/blob/develop/docs/sphinx/internals/audio_backends.rst

[gavv]

Unassigning, so that someone else could work on it.

Abandoned PR: #714